1. Technical Field of the Invention
This invention relates to a method for the recovery of dimethyl ether formed during the manufacture of methyl tertiary butyl ether. This invention more particularly relates to a method for the manufacture and purification of methyl tertiary butyl ether and dimethyl ether. Still more particularly, this invention relates to a method for the manufacture of methyl tertiary butyl ether and dimethyl ether from tertiary butyl alcohol, isobutylene and methanol and for the separate purification of the methyl tertiary butyl ether and dimethyl ether formed by the reaction. In particular, this invention relates to a method for the manufacture of methyl tertiary butyl ether and dimethyl ether from tertiary butyl alcohol, isobutylene and methanol and for an improvement in the separate purification of the methyl tertiary butyl ether and dimethyl ether formed during the reaction.
2. Prior Art
The preparation of methyl tert-butyl ether from methyl and tert-butyl alcohols is discussed in S. V. Rozhkov et al., Prevrashch Uglevodorodov, Kislotno-Osnovn. Geterogennykh Katal. Tezisy Dokl., Vses. Konf., 1977, 150 (C. A. 92:58165y). Here the TBA and methanol undergo etherification over KU-2 strongly acidic sulfopolystyrene cation-exchangers under mild conditions. This reference contains data on basic parameters of such a process.
In U.S. Pat. No. 5,354,912 a process is provided wherein by-product isobutylene formed when methanol is reacted with tertiary butyl alcohol is further reacted downstream of the tertiary butyl alcohol etherification reaction zone with methanol to form a reaction product comprising methyl tertiary butyl ether and dimethyl ether and wherein the methyl tertiary butyl ether formed by the reactions is purified by the removal of impurities, including di-methyl ether.
In U.S. Pat. No. 4,144,138 (1979) to Rao et al., there is disclosed a method for recovering methyl tertiary butyl ether from an etherification reaction effluent by azeotropic distillation to recover a methanol-ether azeotrope overhead which is water-washed to give pure ether raffinate, the latter being azeotropically distilled to yield ether-methanol overhead which is recycled to water washing.
Kruse et al. U.S. Pat. No. 5,243,091, entitled "Method for the Manufacture and Recovery of Methyl Tertiary Butyl Ether", discloses a method for the preparation of methyl tertiary butyl ether wherein tertiary butyl alcohol is reacted with methanol to provide a reaction product comprising methyl tertiary butyl ether and by-product isobutylene and wherein the by-product isobutylene is reacted with methanol to provide additional methyl tertiary butyl ether and also a method for the purification of the methyl tertiary butyl ether.
Gupta U.S. Pat. No. 5,292,964 discloses a process for the manufacture of methyl tertiary butyl ether from tertiary butyl alcohol and methanol wherein tertiary butyl alcohol is reacted with methanol in a primary reaction zone to provide a reaction product comprising methyl tertiary butyl ether, unreacted tertiary butyl alcohol, unreacted methanol and water, wherein the reaction product is separated in a distillation zone into a lighter fraction comprising substantially anhydrous methanol and methyl tertiary butyl alcohol and a heavier fraction comprising tertiary butyl alcohol, methanol and water, and wherein the lighter fraction is charged to a finishing reactor wherein the methanol is reacted with isobutylene to form additional methyl tertiary butyl ether.
Trubac U.S. Pat. No. 4,814,517 discloses a modified method for the purification of methyl tertiary butyl ether manufactured from methanol and isobutylene wherein a distillate overhead stream obtained during the purification of the methyl tertiary butyl ether is passed in liquid phase sequentially through a bed of silica gel to removal methanol and a bed of a zeolite molecular sieve to remove dimethyl ether.